Piperlongumine combined with vitamin C as a new adjuvant therapy against gastric cancer regulates the ROS–STAT3 pathway

OBJECTIVE: To investigate the effects of piperlongumine (PL) and vitamin C (VC) on signal transducer and activator of transcription 3 (STAT3) signalling in gastric cancer cell lines. METHODS: In vivo tumour xenograft anticancer assays were undertaken to confirm the anticancer activity of PL. Cell viability, flow cytometry and Western blot assays were undertaken to evaluate the anticancer effects of PL, VC and combinations of PL and VC in AGS and KATO III cells. RESULTS: Both PL and VC induced apoptosis and inhibited cell proliferation in AGS and KATO III cells. These effects were dependent on reactive oxygen species (ROS). PL effectively suppressed STAT3 activation while VC caused abnormal activation of STAT3. The combination of PL and VC exhibited a stronger apoptotic effect compared with either agent alone. PL reversed the abnormal activation of STAT3 by VC, which could be a key to their synergistic effect. CONCLUSIONS: PL combined with VC exhibited a stronger anticancer effect by regulating the ROS–STAT3 pathway, suggesting that this combination might be a potential adjuvant therapy for gastric cancer.